Network functions virtualization (NFV) adapts network node functions to a virtualized environment. Network Function (NF) is a building block within an operator's network infrastructure, which has well defined external interfaces and a well-defined functional behavior. A VNF (VNF) provides exactly the same functional behavior and interfaces as the equivalent Network Function, but is deployed in a virtualized environment. An orchestrator is software which operates, manages and automates a distributed NFV Infrastructure. The orchestrator has control and visibility of all VNFs running inside the NFV Infrastructure.
VNFs with multiple network interfaces are difficult to orchestrate due to orchestrator limitations. Some orchestrators, for example, do not allow a VNF with two network interfaces on the same subnet. Several network appliances available today utilize multiple network interfaces. These multiple interface appliances, when virtualized, may present difficulties in orchestration.